The business has been detecting such frauds for more than a century and we are confident this is a crime that is in decline. Any losses are certainly far below the figure claimed in your story "Millions lost in massive stamp fraud" (18 October).
The Royal Mail employs a wide variety of security measures to prevent stamp fraud. A key safeguard is a special phosphorous marking on each stamp. "Washing" stamps to remove the postmark affects the phosphor and even though a "washed" stamp may, to the naked eye, look as though it has not been franked, in practice tampered stamps with missing or damaged phosphorous markings are detected by the sophisticated technology now used to automatically read mail.
Post Office Security and Investigation Services